In manual shift transmissions, automated manual shift transmissions and dual-clutch transmissions, according to the prior art gears are engaged or preselected by means of conventional claw elements or synchronizers. In such cases, when two gear transmission ratios are adjacent and on one shaft, depending on the position of the shift actuation element one or the other of these two adjacent transmission ratios can be engaged or coupled to the shaft, or in the neutral position of the shift actuation element both gear transmission ratios can be disengaged.
In some transmission designs, for example dual-clutch transmissions, owing to the arrangement of the transmission ratios it is necessary, when the shift actuation element is in a neutral position, for the two adjacent gear transmission ratios on one shaft both to be shifted to be able to preselect a gear, because of the design. For such transmission designs conventional synchronizers and claw-type shift elements cannot be used, since with such elements the shifting sleeve can always engage only one gear and in the neutral position both gears are disengaged. Below, examples of such transmission designs are described briefly.
For example, a transmission of the type is known from DE 10232831 A1 by the present applicant. The known dual-clutch transmission, which has a countershaft structure, comprises a driveshaft which can be coupled, via a first clutch, to a shaft of a first part-transmission and, via a second clutch, to a shaft of a second part-transmission, the part-transmissions respectively providing different transmission ratios by means of auxiliary transmissions which can be activated by synchronizers. In this case, for synchronization of a shift element of the respective first auxiliary transmission the corresponding clutch of each part-transmission can be actuated appropriately; in addition, for each part-transmission at least one synchronization clutch is provided.
From DE 10232835 A1 by the present applicant a dual-clutch transmission for a motor vehicle is known, which comprises at least two transmission groups with shafts, shift elements and gearwheels, such that the transmission groups can be connected in the force flow to a common driveshaft by means of shift-under-load clutches associated with the transmission groups. In this known transmission each transmission group is so configured that it comprises at least two main branches, and the main branches of each transmission group have gearsets downstream from them via which, by means of shift elements, a connection can be formed to a common output gearwheel of a drive output shaft.
Furthermore, from DE 3233931 C2 a power take-off for a transmission with an incorporated dual clutch is known, such that the power take-off comprises a first transmission mechanism connected or locked to the main take-off shaft and a second transmission mechanism locked or connected to the main running shaft as well as a clutch device, which works in such manner that the transmission mechanisms can be selectively coupled in driving connection with the take-off transmission shaft.